Heating, ventilation, and/or air conditioning (HVAC) systems are often used to control the comfort level within a building or other structure. Such HVAC systems typically include an HVAC controller that controls various HVAC components of the HVAC system in order to affect and/or control one or more environmental conditions within the building.
Many HVAC controllers have a wall plate that is separable from an HVAC controller body. The wall plate is typically secured to a wall in the building, and then the HVAC controller body is secured to the wall plate. When the wall plate is secured to the wall, wires extending from an HVAC system often exit the wall through a roughly-formed hole that is frequently larger than is strictly necessary to accommodate the wires themselves. In some cases, particularly when the fan of the HVAC system is running and/or when the fan cycles on and off, there can be air pressure changes within the wall relative to the air pressure in the room, meaning that positive or negative air currents may form in and near the hole in the wall.
In some embodiments, air can be pulled out of an HVAC controller in a negative wall pressure case. It will be appreciated that air pressure in the wall can be expressed as a negative pressure condition, i.e., the pressure in the wall is less than the ambient pressure, or a positive pressure condition, i.e., the pressure in the wall is greater than the ambient pressure. In some cases, for example, a negative wall pressure condition can result if an installer runs HVAC control wires through a wall cavity being used as part of the return duct system.
Air currents, whether resulting from a positive wall pressure condition or a negative wall pressure condition, can potentially interfere with temperature readings taken by one or more temperature sensors within the HVAC controller body, particularly when the air currents are allowed to approach and/or enter or exit the HVAC controller body. In some instances, when an HVAC controller is configured to compensate the internal temperature readings taken by the one or more internal temperature sensors to account for heat generation by components within the HVAC controller body, such air currents can interfere with the temperature compensation algorithm, which can reduce the temperature control accuracy of the HVAC controller, reduce the comfort provided to the user, and/or reduce the energy efficiency that can be achieved by the HVAC system.